Mycology in mycrobiology

1. Introduction to mycology and
classification
Dr Mtebe Majigo
Dept Microbiology and
Immunology

2. Objectives
 General characteristics
 Structure of fungi
 Classification of fungi

3. Mycology
 Study of fungi
 Organism that contain true nuclei
(eukaryotic)
 Devoid of chlorophyll
 Absorb all nutrients from the
environment, especially from decaying
organic matter

4. 4
Importance
 beneficial impact
 decomposers
 industrial fermentations
 fermented foods and beverages
 steroids, antibiotics and other drugs
 research
 model eucaryotic organisms
 detrimental impact
 major cause of plant diseases
 cause of many animal, including human, diseases

5. Characteristics
 Eukaryotic – a true nucleus
 Do not contain chlorophyll
 Have cell walls
 Produce filamentous structures
 Produce spores

6. Reproduction
 asexual reproduction
 transverse fission
 budding
 spore production
 sexual reproduction
 involves union of compatible nuclei followed
by formation of sexual spores (zygospores,
ascospores, or basidiospores)

8. 8
Sexual reproduction
 zygote formation
 several mechanisms
 fusion of gametes
 fusion of gametangia
 gamete-producing bodies
 fusion of hyphae

9. Nutritional adaptations
 Low pH
 Most are aerobic
 Osmotic pressure
 Low moisture
 Low nitrogen
 Can digest complex carbohydrates

10. MORPHOLGY
 Yeasts
 Hyphae (filamentous fungi, mycelium)
 Septate
 Coenocytic (non-septate)
 Dimorphic
 Yeast
 Mycelium

11. Dimorphic Fungi
 Yeast Form
 Parasitic form
 Tissue form
 Cultured at 37 C
 Mycelial Form
 Saprophytic form
 Cultured at 25 C

12. SPORES
 SEXUAL
 ASEXUAL
 Arthrospore
 Blastospore
 Chamydospore
 Conidia
 Microconidia
 Macroconidia

14. 14
Yeasts
 unicellular fungi
 reproduce asexually, often by budding
 reproduce sexually by formation of spores

17. 17
Molds
 filamentous fungi
 hyphae (s., hypha)
 the filaments of a mold
 may be coenocytic (no cross walls) or have septa
(cross walls)
 mycelium (pl. mycelia)
 bundles or tangled masses of hyphae

18. coenocytic hypha
septate hypha

19. 19
Figure 25.5

20. 20
Dimorphism
 some fungi change from yeast form (Y) to
mold form (M)
 YM shift
 in animals, Y in host and M outside host
 in plants, M in host and Y outside host

22. Classification
 Zygomycetes - ribbon-like aseptate
hyphae; sexual and asexual
 Ascomycetes - septate; sexual and asexual;
produce asci
 Basidiomycetes - septate; sexual;
mushrooms; club fungi
 Deuteromycetes (Fungi Imperfecti) – no
sexual stage; many common pathogens

23. Division of fungi
23

24. 24
Zygomycota
 zygomycetes
 form coenocytic hyphae containing numerous
haploid nuclei
 most are saprophytes
 a few are plant and animal parasites
 some of industrial importance
 foods, antibiotics and other drugs, meat tenderizer,
and food coloring

26. 26
Ascomycota
 ascomycetes – sac fungi
 during sexual reproduction produce ascus (pl., asci)
containing haploid ascospores
 considerable human impact
 food spoilage and plant diseases
 edible mushrooms, and food and beverage production
 research
 can be filamentous or yeast form
 filamentous forms have septate hyphae and asexual
reproduction by conidiospores

28. 28
Basidiomycota
 basidiomycetes – club fungi
 during sexual reproduction form basidium
 human impact
 decomposers
 edible mushrooms
 pathogens of humans, other animals, and plants
 e.g., Cryptococcus neoformans – cryptococcosis
 systemic infection, primarily of lungs and central nervous
system

30. 30
Deuteromycota
 deuteromycetes – Fungi Imperfecti
 no known sexual reproduction
 most are terrestrial; a few are aquatic
 most are saprophytes or plant parasites
 some parasitic on other fungi
 some predatory
 human impact
 some human pathogens
 ringworm, athlete’s foot, histoplasmosis
 production of antibiotics, foods, and organic acids
(e.g., citric acid)

31. MYCOTIC DISEASES
1. Hypersensitivity
 Allergy
2. Mycotoxicosis
 Production of toxin
3. Mycetismus (mushroom poisoning)
 Preformed toxin
4. Infection

32. Fungal diseases
 Mycoses
 Systemic
 Subcutaneous
 Cutaneous
 Superficial
 Opportunistic pathogens

33. Diagnosis
1. Wet Mount
2. Skin test
3. Serology
4. Fluorescent antibody
5. Biopsy and histopathology
6. Culture